1. Field of the Invention
The present invention relates to a soldering iron having a nozzle, which provides an inert gas passage, fixed in the vicinity of the tip of an electric soldering iron, and protecting the iron tip from oxidation due to high temperature, and protecting both a member to be soldered, and solder made of a flux cored solder alloy and flux from oxidation, by jetting an inert gas from the nozzle.
2. Description of the Related Arts
It is common practice that connecting and bonding are carried out by soldering in industries, especially electronic industries. The reasons are that an Sn--Pb alloy used for soldering has a low melting point, and its workability is high, and further portions thus connected or bonded have a high reliability.
The soldering method is largely classified into a mass soldering method (collective soldering method) and a manual soldering method.
The mass soldering method is further classified into a flow soldering method in which a printed circuit board (PCB) incorporating IC elements, components, etc. is soldered by being immersed into molten solder, and a reflow soldering method (SMT) in which heated soldering is carried out after solder paste obtained by blending solder grains and flux together with a binder material is printed to a soldering portion on a printed circuit board(PCB), wherein either of them has a feature in that a number of points are soldered almost at the same time.
On the other hand, the manual soldering method is mainly carried out by using a soldering iron. In this case, although it is impossible to solder a number of points at the same time, this method has been employed since a long time ago, and there is an advantage in that anyone is easily able to perform soldering. The manual soldering by using a soldering iron is still required for correcting or retouching defects produced by the mass soldering method.
Hereinafter, the present invention relates to an electric soldering iron.
In addition, FIG. 1 and FIG. 2 show an electric soldering iron according to the prior art, wherein FIG. 1 shows disassembled parts of a soldering iron, and FIG. 2 shows an assembled iron.
As shown in these drawings, a prior art soldering iron is such that, after a cap nut 1 is attached to a protection pipe 2, a hollow iron tip 3 is attached to a ceramic heater 4 and is further attached to a nipple 5, and they are tightened and fixed with the cap nut 1. And, heat coming from the ceramic heater incorporated in the iron tip portion is transmitted to a copper iron tip 3, whereby the iron tip is heated.
As a general method of using an electric soldering iron, there is a soldering method in which an Sn--Pb based alloy called flux cored solder is melted on an iron tip, the melted solder on the iron tip is brought to a soldering position, such as a component of a workpiece, and another method in which a workpiece is preheated by using an iron tip and flux cored solder is supplied to the workpiece after it is sufficiently heated. In either case, in view of the working efficiency, it is desirable that the iron tip temperature is approximately 150.degree. C. above the melting point of a solder alloy to be used. For example, since the melting point of conventional Sn-37% Pb eutectic solder is 183.degree. C., the temperature of the iron tip is set from 330 through 350.degree. C. in order to carry out the work, wherein soldering carried out within the temperature range above has no problem.
However, in recent years, Pb which is a main constituent of Sn--Pb solder has been regarded as one of the greatest causes of water pollution and no longer seems to be used in solder alloys. Waste products such as those of domestic electrical appliances and automobiles are illegally dumped, and Pb flows out from printed circuit boards in the internal components, by external causes such as acid rain, etc., and contaminates underground water by permeating soil. This has been considered as a large social problem in the United States of America, and a Pb-free environment is highly desired worldwide.
Various types of Pb free solder have been developed until now. However, since pure Sn, Sn-3.5% Ag, Sn--Bi--Ag, etc., are based on Sn-based alloys, the range of the melting point is from 210 to 232.degree. C. and is higher by 30 to 50.degree. C. than that of conventional Sn-37% Pb solder. Therefore, the operating temperature becomes higher, wherein unless the iron tip temperature is raised above 350.degree. C., sufficient soldering performance cannot be obtained.
However, the operating environment where a soldering iron tip with a temperature exceeding 350.degree. C. is used becomes considerably different from that where a conventional soldering iron tip has been used. In such temperature range, flux is deteriorated and oxidation of a soldering iron tip occurs if it is made of pure copper or copper alloys. Therefore, if Pb-free solder is used, the soldering performance may be remarkably reduced. This is an adverse influence caused by ambient oxygen. It is therefore an object of the present invention to solve such problems by installing a nozzle which jets an inert gas to a soldering iron tip.